Jerusalem Talmud Yevamot 5:7

משנה: חָלַץ וְחָלַץ חָלַץ וְעָשָׂה מַאֲמָר נָתַן גֵּט וּבַעָל אוֹ בָּעַל וּבָעל אוֹ בָּעַל וְעָשָׂה מַאֲמָר. נָתַן גֵּט וְחָלַץ אֵין אַחַר חֲלִיצָה כְּלוּם. בֵּין יָבָם אֶחָד לִשְׁתֵּי יְבָמוֹת בֵּין שְׁנֵי יְבָמִים לִיבָמָה אַחַת. MISHNAH: If he performed ḥaliṣah with both of them⁸⁴This Mishnah deals with the case of one levir and two sisters-in-law. It is understood that in any group, the first action refers to the first widow, the second to the second, but not both to one woman sequentially., performed ḥaliṣah and “bespoke”⁸⁵The second ḥaliṣah is void; the second widow is not forbidden for a Cohen nor are her close relatives forbidden to the levir., gave a divorce document and copulated⁷¹The intercourse was illegal, he may not keep his wife and has to divorce her. The first one needs a rabbinic divorce for her rabbinic “bespeaking”., or copulated with both of them⁸⁶He is married to the first; the relationship with the second was incestuous and no marital relationship was established with her., or copulated and “bespoke”⁸⁷The act of “bespeaking” is legally nonexistent., gave a divorce document and performed ḥaliṣah⁸⁸Case already treated in Mishnah 5:3., nothing comes after ḥalîṣah, whether there are two sisters-in-law and one levir or two levirs with one sister-in-law⁸⁹The second case is treated at the beginning of the next Mishnah in a repetetive manner..